Physicochemical properties and antimicrobial activity of Roselle (Hibiscus sabdariffa L.).

BACKGROUND: The therapeutic action of a plant depends on its chemical constituents. In this study, experiments were carried out in order to evaluate the effect of extraction conditions on the antioxidative and antimicrobial activities of Roselle (Hibiscus sabdariffa L.). RESULTS: Roselle was found to be rich in malic acid, anthocyanins, ascorbic acid and minerals, especially Ca and Fe, but low in glucose. More than 18 volatile compounds were identified by gas chromatography and gas chromatography-mass spectrometry. This herb, which is rich in phenolic compounds and displays DPPH radical scavenging activity, could be a good source of natural antioxidants. The antimicrobial activity of the Roselle water and ethanol extracts was tested with Bacillus subtilis (ATCC6633), Staphylococcus aureus (ATCC6538) and Escherichia coli (ATCC 8739). The inhibition of the Roselle ethanol extract against B. subtilis and S. aureus was slightly higher than that of water extract but this difference was not significant. However, E. coli was strongly inhibited by the Roselle water extract at concentrations of 25 and 50 mg mL(-1) as determined by a paper disc method. CONCLUSION: The obtained results indicated that antioxidant and antimicrobial activity was related to different methods of extraction and Roselle extracts could be a source of therapeutically useful products.

Roselle (Hibiscus sabdariffa L.) and soybean oil effects on quality characteristics of pork patties studied by response surface methodology.

Response surface methodology was used to investigate the effect and interactions of processing variables such as roselle extract (0.1-1.3%), soybean oil (5-20%) on physicochemical, textural and sensory properties of cooked pork patties. It was found that reduction in thickness, pH, L* and b* values decreased; however, water-holding capacity, reduction in diameter and a* values increased, respectively, as the amount of roselle increased. Soybean oil addition increased water-holding capacity, reduction in thickness, b* values of the patties. The hardness depended on the roselle and soybean oil added, as its linear effect was negative at p<0.01. The preference of color, tenderness, juiciness, and overall quality depend on the addition of roselle and soybean oil. The maximum overall quality score (5.42) was observed when 12.5 g of soybean oil and 0.7 g of roselle extract was added. The results of this optimization study would be useful for meat industry that tends to increase the product yield for patties using the optimum levels of ingredients by RSM.